In the following sentence, choose the most appropriate preposition to replace the bracketed word so that the idiomatic expression is correct: The workers are bent (on) getting a full months pay as bonus.

Introduction / Context:
This question checks your understanding of English prepositions and idiomatic expressions. Many phrases use fixed prepositions that cannot be changed without sounding unnatural. In competitive exams, these idiomatic combinations are tested frequently. The sentence here talks about workers who are strongly determined to receive a full month's pay as a bonus. You must select the preposition that makes the expression bent upon or bent on correct and idiomatic in standard written English.

Given Data / Assumptions:

• Sentence: The workers are bent (on) getting a full months pay as bonus.
• We need to decide which preposition fits best after bent.
• Options: for, upon, to, no improvement.
• The intended meaning is that the workers are determined to get the bonus.

Concept / Approach:
Bent on and bent upon are both idiomatic expressions in English that mean determined to do something or very strongly inclined towards doing it. However, standard formal usage, especially in older and exam oriented English, often prefers bent upon when we talk about people being firmly resolved to achieve something. The phrase bent for is incorrect in this sense, bent to is not used this way, and no improvement would keep bent on, which is acceptable in modern usage but the question expects the more classic exam friendly collocation bent upon getting. Therefore upon is the best choice here.

Step-by-Step Solution:
Step 1: Identify the idiom pattern: be bent on or be bent upon something means to be determined to do it. Step 2: Recognise that the sentence describes determination: the workers are strongly focused on getting the full pay as bonus. Step 3: Examine the options. For expresses purpose or benefit but not this strong determination in idiomatic form. Step 4: Upon appears in the well known collocation bent upon, which matches our required meaning exactly. Step 5: To does not create a standard expression here, and choosing no improvement would miss the chance to use the more precise idiom.

Verification / Alternative check:
Consider how the sentence sounds with each option. The workers are bent for getting a full months pay as bonus sounds wrong. The workers are bent to getting a full months pay as bonus is also incorrect. The workers are bent on getting a full months pay as bonus is used in conversational English, but exam setters often look for bent upon when they highlight the idiom. The workers are bent upon getting a full months pay as bonus sounds natural and matches formal idiomatic usage. This confirms that upon is the best answer in this exam context.

Why Other Options Are Wrong:

• for: Bent for does not form a standard idiomatic phrase for strong determination, so it is incorrect here.
• to: Bent to also fails to convey the idiomatic meaning and is ungrammatical in this context.
• no improvement: Although bent on is possible in modern English, the question expects the more formal and widely taught bent upon in exam oriented grammar, so no improvement is not the best choice.

Common Pitfalls:
A common mistake is to rely only on partial familiarity with an expression. Students may have heard bent on without noticing that textbooks often emphasise bent upon. Another pitfall is choosing no improvement whenever the sentence seems understandable, even if a more accurate idiom exists. To handle such questions well, it is helpful to read from good grammar books and note fixed prepositional patterns. Regular exposure to high quality English, such as editorials and reference texts, reinforces these combinations and makes such questions easier.

Final Answer:
The correct improvement is upon, so the idiomatic expression becomes The workers are bent upon getting a full months pay as bonus, expressing strong determination in standard English.